Latest revision as of 18:59, 18 February 2012

General Purpose I/O

The Raspberry Pi allows peripherals and expansion boards (such as the upcoming Gertboard) to access the CPU by exposing the inputs and outputs. The production board has a 26-pin 2.54mm (100mil) expansion header, arranged in a 2x13 strip. They provide 8 GPIO pins plus access to I2C, SPI, UART), as well as +3V3, +5V and GND supply lines. Pin one is column 0 on the bottom row.

Voltages
Voltage levels are 3v3. There is no over-voltage protection on the board - the intention is that people interested in serious interfacing will use an external board with buffers, level conversion and analog I/O rather than soldering directly onto the main board.

I2C
It is also possible to reconfigure some of the pins to provide a second I2C interface.

Boot Messages

Kernel boot messages go to the UART (serial port) at 115200bps.

Power pins
Maximum permitted current draw from the 3v3 pin is 50mA.
Maximum permitted current draw from the 5v pin is the USB input current (usually 1A) minus any current draw from the rest of the board.

• On the production board, all the UART, SPI and I2C pins can be reconfigured as GPIO pins, to provide a total of 17 GPIO pins.
• At least some of the GPIO pins support PWM.
• GPIO voltage levels are 3V3 and are not 5V tolerant.
• Each GPIO can interrupt high/low/rise/fall/change.
• It is also possible to reconfigure some of the pins to provide an ARM JTAG interface.
• It is also possible to reconfigure some of the pins to provide an I2S (hardware mod may be required) or PCM interface.